1. Field of the Invention
This invention relates to a bulk container and a removable liner for storing and shipping fluid and semi-fluid materials in bulk, such as fluid and semi-fluid adhesives, polyester resins or the like, paints, photosensitive lithographic compounds, foodstuffs, etc.
In storing and shipping fluid and semi-fluid materials, it is preferable to utilize containers, such as drums, intermediate bulk containers, and bulk containers varying in size from about 30 to 1000 gallons. Due to the expense in manufacturing such large containers, it is preferable to reuse the containers as often as possible. However, if the material is stored directly inside the container, the container would desirably need to be cleaned after each use. Such cleaning can be very difficult (and therefore costly) to carry out and sometimes impossible to accomplish effectively, depending upon the type of material used. With some materials, if a delay is anticipated before cleaning can be effected, it is necessary to fill the container completely with some type of solvent, such as water or acetone, after the supply of the material is exhausted, so that the residual material will not harden against the interior walls of the container and make such cleaning even more difficult. Some solvents, such as acetone, may be classified as a hazardous material that requires strict disposal procedures, thereby making cleaning even more costly.
Furthermore, some materials may be more chemically incompatible with the container, depending upon the composition of the container. Likewise, some materials may chemically react with the container and contaminate the stored material. Moreover, some materials are not authorized to be used in food grade applications.
In order to resolve these problems, it has been proposed to coat the interior walls of bulk containers with a composition that will prevent undesired chemical reactions between the stored material and the interior container walls, such as corrosion, and to provide a more readily cleanable surface. However, such coating involves a complex process and the integrity of the coating cannot always be guaranteed. If an undetected pin hole exists in the coating, an undesirable chemical reaction between the stored material and the container may occur, thus contaminating the entire contents of the container. Also, the walls of the container may corrode and even rupture. In addition, it is still somewhat difficult to clean the interior of the container, especially if there is limited access to it.
It has also been proposed to construct bulk containers out of different materials, specifically selected according to the composition of the material to be stored. However, such a strategy is costly, especially if containers for a wide variety of materials are desired. Also, some materials for forming the container may have better strength attributes than other materials, thus requiring different wall thicknesses.
Further, an unlined container must be painstakingly cleaned if it is desired to be reused--especially if it is to be used for different contents.
Therefore, it is generally preferred to utilize a removable liner in the bulk containers. Removable liners can protect the container from corrosion by the stored material and can prevent contamination of the stored material by acting as a barrier between the container and the stored material. Further, when the supply of stored material is depleted, the liner, being less massive and, therefore, relatively inexpensive, can be removed and simply disposed of. A new liner can then be inserted and the bulk container can be reused without any need for cleaning. The bulk container can be mass-produced using one preferred material, and one set of parameters for wall thickness, whereas several liners can each be made of a different material, depending upon the type of material to be shipped or stored. That is, each bulk container can be used, during its lifetime, for storing more than one type of liquid because only the liner need be changed.
A typical liner includes an inlet fitment and a discharge fitment and there is a need to connect the discharge fitment of the liner with a discharge port of the bulk container. An adapter has been proposed for connecting the discharge fitment of the liner with the discharge port of the bulk container. One type of adapter that had been designed by inventors of the present invention is shown in FIG. 9 of the drawings accompanying this specification. Referring to FIG. 9, adapter 100 includes an inner cylinder 102 and an outer cylinder 104. The outer cylinder 104 is connected to the inner cylinder 102 via a flange 106. On a first or proximal end of the inner cylinder a first set of male, tapered threads 108 is provided. 0n the second or distal end, a second set of male, tapered threads 110 is provided. In addition, a third set of male, tapered threads 112 is provided on the outer cylinder 104. (The tapers are not shown to scale in the drawings. They can be made to pipefitting standards.) In installing the liner in the bulk container, the adapter 100 must be aligned with the discharge fitment on the liner as it is screwed into the discharge port of the bulk container. It may be necessary to have an aide crawl into the container and hold the discharge fitment in position. The installer then rotates the adapter 100 to simultaneously engage the threads 108 with the discharge fitment and the threads 104 with female threads on the discharge port on the bulk container. After the adapter is tight, a valve can be installed by engaging with threads 110 from outside the bulk container.
Such an assembly process proved tedious and difficult to accomplish. In many bulk containers access can be very limited. Further, simultaneously engaging the threads of the discharge fitment on the liner and the threads of the discharge port with the different sets of threads of the adapter is very difficult if the components are not perfectly aligned, and sometimes requires several attempts. After the adapter is disconnected, residual stored material may leak through the discharge fitment of the liner and drip into the bulk container before the liner can be withdrawn, thereby requiring cleaning.
Furthermore, a typical discharge fitment on a flexible liner, which is in essence a spout to which a valve can be attached, is relatively long in comparison to its diameter. Therefore, when such a discharge fitment is engaged with the adapter 100, which in turn is threaded in the discharge port of the bulk container, the portion of the liner surrounding the discharge fitment must necessarily be disposed a significant distance back from the rigid wall of the container. When the container is filled, the static pressure within the liner due to the weight of the filled material tends to stretch that region of the liner toward the container walls, thereby giving rise to a potential of tearing the unsupported liner at that location.